Read the excerpt from Harry Potter and the Sorcerer's Stone:
"Great Uncle Algie came round for dinner, and he was hanging me out of an upstairs window by my ankles when Great Auntie Enid offered him a meringue and he accidentally let go. But I bounced---all the way down to the garden and into the road. They were all really pleased, Gran was crying she was so happy.
Based on the description above, why is Gran Happy?